Passive-active transition behavior of 304 stainless steel

The passive-active transition behavior of a 304 stainless steel was investigated by observing the self-activation behavior and nano-scale galvanostatic cathodic reduction experiment. The self-activation time, tau(0) was dependent remarkably on concentration of sulfuric acid. It was appeared that applied nano-scale cathodic current density dissolved the passive film on a 304 stainless steel surface and shortened the activation time in galvanostatic cathodic reduction experiments. The applied cathodic current density was proportional to the reciprocal of activation time. From this linear relationship, the rate of the self-activation process, i(0) was obtained. The i(0) increased with increasing H2SO4 concentration. And i(0) also increased with increasing passivation potential and passivation time. The stability of passive film increased in accordance with increasing tau(0) and decreasing i(0). Therefore, it was concluded that the stability of passive film on austenitic stainless steel is evaluated by the kinetic parameters of the self-activation rate i(0) and the self-activation time, tau(0).